Cox,32,joins from Southend United - the League One club where Milligan now plays - having scored just twice in 19 appearances this season. He has been the club's top scorer for the last three seasons,with a total of 45 goals and 26 assists in 172 games.
Cox has spent most of his career in England's second and third divisions but spent two seasons,between 2010 and 2012,playing for West Bromwich Albion in the Premier League,and has represented his country on 30 occasions.
On paper,he appears to be a vast improvement on Meier,who has been shown the door by the Wanderers after a dismal 12 games for the club.
The Wanderers have still not confirmed Meier's departure but will need to axe one of their five foreigners to make way for Cox. Meier has also not responded to inquiries from theHerald.
Meier,37,was not included in Western Sydney's squad for Sunday's clash with Perth Glory at Bankwest Stadium and not listed as unavailable due to injury.
The fact that recruitment moves of this magnitude are being made in the January window suggests the under-fire Babbel still has the backing of chairman Paul Lederer and has been given the opportunity to reverse Western Sydney’s fortunes.